One of the most common fatal diseases is vascular disease, in particular cardiac infarct. This is caused by diseases of the coronary arteries, which cause what is known as arteriosclerosis. With such diseases, deposits (atherosclerotic plaque) on the vessel wall cause a reduction in the diameter of the vessel, which can result in the blockage or one or a plurality of coronary arteries. It is now recognized that the risk of cardiac infarct is not primarily due to the reduced vessel diameter. Rather it is a question of whether the thin protective layer covering the arteriosclerotic deposits holds. If it breaks, platelets tend to accumulate at the break, closing the vessel completely within a short time, thereby causing the cardiac infarct. If coronary angiography shows serious narrowing or stenosis in the coronary arteries, causing angina pectoris, associated with restricted performance and a threat to the life of the patient, depending on the individual case either a bypass operation or a balloon dilatation, also known as percutaneous transluminal coronary angioplasty (=PTCA), is carried out. Generally the PTCA procedure is carried out. During this the constrictions in the coronary arteries are widened using a so-called balloon catheter. This catheter has a balloon towards the front of the area of its tip, said balloon generally being of a type that can be inflated with a salt solution and being inflated at the site where the vessel is widened. So that the widened vessel does not return to its original state after dilatation, a so-called stent is inserted into the widened section of the vessel after dilatation. This stent is a cylindrical, generally metal, mesh grid, which is shaped in a plastic manner using the balloon and is held against the inner wall of the vessel.
The usual treatment method first provides for diagnosis of the stenosis by means of a cardiac catheter examination as part of a coronary angiography procedure with contrast agents subject to X-ray control. To this end a catheter is inserted into the coronary vessels and the contrast agent is injected into the coronary vessels via the catheter. The catheter is then removed. The disadvantage of this method step is that only the vessel diameter that can be used by the blood flow or the constriction is shown as a silhouette. No information is available about the deposit, in particular its thickness or the extent of the inflammation process. After the first diagnosis of stenosis, the balloon catheter is inserted subject to X-ray control and the vessel is widened. The catheter is then removed. A further catheter is now inserted to position the stent. This is fed in up to the point of the vessel to be treated, after which the stent is positioned as described by inflating the catheter and the catheter is then removed again. This also takes place under X-ray control, with the disadvantage that the stent cannot easily be seen in the angiography X-ray image, i.e. the possibility of verifying whether the stent has been positioned correctly is very limited.